Patented Dec. 6, 1938 2,139,325 UNITED STATES 2,139,325PATENT OFFICE MANUFACTURE OF 4-AMINO-AZO-BENZENE 4-SULPHONCAC) Charles B. Biswell and Walter W. Wirth, Woods town, N. J., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del, a cor poration of Delaware No Drawing. Application February 2, 1937, Serial No. 123,602 6 Claims. (CI. 260-205) This invention relates to the manufacture of and still other objects of the invention will be 4-amino-aZO-benzene-4'-sulphonic acid, and apparent from the following more detailed de more particularly to processes of making the Scription. product by the acid hydrolysis of the alkali salt Y of omega-Sulphonic-acid of 4-alkyl-amino-azo The objects of the invention are accomplished generally by operating directly upon the alkali 5 benzene-4'-sulphonic acid, and to a new im metal Salt of the Omega-sulphonic-acid of a proved product. 4 - alkyl -amino-aZO-benzene-4'-sulphonic acid. Heretofore 4-amino-azo-benzene Sulphonic This salt may be made by coupling p-dia Zo-ben acid was prepared from the Omega Sulphonic Zene Sulphonate and an alkyl-aniline-omega-SO acid of 4-methylamino-azo-benzene-Sodium Sul dium-Sulphonate in sodium acetate solution by 10 phonate by a process in which the 4'-SO3H methods known to the art, but any method of group and the -CH2-SO3Na group Were replaced naking this compound and other alkali metal With hydrogen by a hydrolytic decomposition re Salts of the compound can be used. - 35 action. This process consisted of mixing the so The resulting alkali metal salt of the omega dium salt of the omega-sulphonic-acid of 4 sulphonic-acid of 4-alkyl-amino-azo-benzene 15 methyl-amino-azo-benzenesulphonic acid with a 4'-sulphonic-acid is hydrolyzed to 4-amino-azo mineral acid at Ordinary atmospheric tempera benzene-4'-sulphonic-acid by adding the coupling tures, at which temperature the first part of the suspension or solution to a hot solution of a non process was conducted at a relatively slow rate oxidizing mineral acid, such as hydrochloric or 2 for a period of time. Thereafter the acidified reaction medium was heated to finish the reac sulphuric acid which is heated to a Sufficiently 20 tion and attain the maximum yield of product. high temperature, say about 80° to about 105° C., However, this process gave relatively low yields which acid is present in sufficient excess, Say of the product. It produced a product contain about 3 to 20 equivalents of acid so that the re ing foreign substances. Which resulted in dyes action takes place at a highly rapid rate from having poor discharge properties when they Were the start of the reaction, the alkali metals are 25 used as intermediates in making the dyes, namely combined with the acid and the impurities in that the discharged portions of the dyed fabric formed during the reaction are readily and con had a dull yellowish or brownish shade. AC tinuously dissolved as they are formed and re 30 cording to other prior art processes, the hydro moved in solution by the acidic reaction medi lytic decomposition of the -CH2-SO3Na WaS um. The quantity of acid is regulated So as to 30 carried out in the presence of alkalies, such as provide an excess of acid in the final mixture sodium hydroxide. The latter processes gave after the reaction is completed of about 1.5 to somewhat better yields than the former but the about 3.0 grams of the milleral acid per 100 cubic $) characteristics and properties of the products centimeters. The acid concentration is desir ably such that it varies from an initial strength 35 were similar and they produced similar unde of about 8% to a final strength of about 4%. sirable results when they were used as inter The temperature of the acid hydrolysis medium mediates. Even in making these relatively im is kept at the elevated temperature throughout pure products, it was necessary to apply purifi the addition of the coupling maSS. The temper it) cation processes to these products in order to obtain a satisfactory product. Therefore, it is ature may then be dropped to a convenient 40 desirable to provide new processes and improved working temperature, say about 60° C., and the products, both from considerations of yield and precipitated product filtered off and washed. cost of production and from the consideration of Eacample I 45 the quality of the product. It is an object of the present invention to pro (1) Diazotization of Sulphanilic acid: 279.5 lbs. 45 wide a 4-amino-azo-benzene-4'-sulphonic acid of 30% HCl were added to a solution of 195 lbs. product having improved properties. Another of Sodium Sulphanilate (imol), in 1712 lbs. of wa object of the invention is to provide new proc ter, to precipitate free sulfanilic acid. The Sus 50 esses for producing the product economically, pension was cooled to 5 C. by adding ice, and sufficient 30% sodium nitrite Solution was run 50 and in high yield and quality. Another object in to diazotize all of the Sulphanilic acid attem of the invention is to provide processes by means peratures below 10° C. A test for a slight excess of which a purified product can be separated of nitrous acid was maintained for A hour. 171 from the reaction mixture in which it is formed lbs. of hydrated sodium acetate (molecular by simple acts of filtration and Washing. These weight.136.7) were added to make the charge 55. 2 2,139,825 neutral to Congo red indicator and acid to lit as produced by the described prior art methods mus indicator. Ice was added to cool the Suspen was used in the same manner, the discharged sion to 5° C. The total ice used was about portions of the dyed cloth Were always a dull yellow or brownish Color. 980 lbs. Other alkali salts of the omega-sulphonic-acid (2) Coupling to methyl-aniline-omega-sodium of 4-alkyl-amino-azo-benzene-4'-sulphonic acid sulphonate. 215.2 lbs. of 100% methyl-aniline instead of the sodium salt of the compound, such omega-sodium-Sulphonate (molecular weight 209) as the potassium salt can be used. Likewise the in the form of about an 80% paste, were dis various alkyl derivatives can be used, such as the solved in about 1000 lbs. of water. The solution. methyl, ethyl or propyl. For the best results the 0. 10 was cooled to 5 C. With about 900 lbs. of ice. concentration of the acid in the hydrolyzing The diazo suspension made in accordance with reaction medium can be varied from about 3 to (1) was run in and the mass which was still about 20 equivalents of the acid per mol of the slightly acid to litmus was stirred 20 to 25 min hydrolyzed compound, but more or less concen utes to effect complete coupling. The coupled trated acid can be used, the concentration of the 15 5 compound may be represented by the formula acid being chosen with a view to economy of op eration, yield of product and quality of product. Naosch. NH-O-N-N-(D-SON From the latter considerations the temperature (3) Acid hydrolysis of the Omega-sulphonate of the acid may be varied from about 80° C. to about 105 C. 20 20 of 4 - methyl-amino-azo-benzene-4'-sulphonic acid (sodium salt). 3500 lbs., of Water and 690 Still other modifications will be suggested to lbs. of 30% HCl were added to a Wooden tub and those skilled in the art, without departing from heated to 95° C. This solution contained about the spirit and scope of the invention, and it is 5.7 mols of HCl per mol of the compound to be to be understood that no limitations are intended treated. Without. Separating the coupling Com except such as are specifically recited in the 25 25 pound, the coupling mass was run into the hot claims or are imposed by the prior art. dilute acid at such a rate that the temperature We claim: was held at 95-100° C. during the addition. The 1. In a proceSS for manufacturing 4-amino reaction medium can be heated or cooled if nec aZo-benzene-4'-sulphonic acid, the steps which essary to maintain the desired temperature. The comprise heating a Solution of non-oxidizing acid 30 30 temperature was kept at 95-100° C. for 30 min to about 90° C. to about 100° C. adding the utes after the addition was completed and then Sodium Salt of omega-sulphonic acid of 4-methyl the mass was cooled to 60° C. The precipitated amino-aZO benzene-4'-sulphonic acid to the solu. amino-azo-benzene-sulphonic-acid was filtered tion, Said nonoxidizing acid being capable of con off and washed free of mineral acid. verting the alkali metal Sulphonic acid group to 35 35 249.5 lbs. of 100% amino-azo-benzene-sul the Sulphonic acid group and of causing hydro phonic-acid (molecular weight 277.2) in the form lytic decomposition of the alkyl-alkali-metal of a 30-35% hydrous paste were obtained. The Sulphonic acid group, and maintaining the tem yield was 90% of theory, based on the sulphanilic perature of the reaction mixture approximately acid used as the starting material. Within said temperature range until 4-amino 40 40 aZO-benzene-4'-sulphonic acid is formed. Eacample II 2. In a process for manufacturing 4-amino aZo-benzene-4'-sulphonic acid, the steps which For the HCl used in the Sulphanilic diazotiza comprise heating a solution of non-oxidizing acid tion 141 lbs. of 78% H2SO4 were used. The acid to about 90° C. to about 100° C. adding the 45 45 hydrolysis tub was charged with 4000 lbs. of Wa Sodium salt of Omega-sulphonic acid of 4-methyl ter and 440 lbs. of 78% H2SO4, and the solution amino-aZO-benzene-4'-sulphonic acid to the so was heated to 95-98 C. This solution contained lution, Said nonoxidizing acid being capable of about 3.6 mols of H2SO4 per mol of compound converting the alkali metal sulphonic acid group to be treated. The coupling mass was run into to the Sulphonic acid group and of causing hydro 50 50 the heated acid during a period of 4 hour, dur lytic decomposition of the alkyl-alkali-metal ing which time the reaction mass was kept at sulphonic acid group, said acid solution contain 95-98 C. After the coupling mass was added, ing an equivalent of about 3 to about 10 mols of the reaction mass was held at 95-98 C. for A Sulphuric acid per mol of the compound to be hour. It was then cooled to 60° C. and the prod hydrolyzed, and maintaining the temperature of 55 55 luct was filtered off and washed free of mineral the reaction mixture approximately within said acid. The quality of the product and the yield temperature range until 4-amino-azo-benzene were about the same as that obtained in accord 4'-sulphonic acid is formed. ance With Example I. 3. In a process for manufacturing 4-amino The hydrolysis may be represented by the foll aZo-benzene-4'-sulphonic acid, the steps which 60 60 lowing equation: comprise progressively adding an alkali metal sait of the omega-sulphonic acid of a 4-alkyl N-C.N.I.C.S.O.3Na --H2O--HSO-9(4) N-CH-SON a 3. amino-azo-benzene-4'-sulphonic acid to a solu N-CH-NH 4) tion of a non-oxidizing mineral acid which is at --CHO--SOs--Na2SO a temperature of about 90 to about 100° C. and 65 N-CH-SOs (4) Contains an excess of the acid over that which Portions of the products from Examples I and Will convert the alkali metal sulphonic acid II were used to make a red azo dye formed by group in the alkali metal salt to the sulphonic coupling diazotized amino-azo-benzene sulphonic acid group and cause hydrolytic decomposition acid to p-amino-benzoyl-J-acid. The dye was of the alkyl-alkali metal Sulphonic acid group, 70 70 developed on cotton with beta naphthol and then printed with a discharge paste containing sodium Whilst continuously hydrolyzing said salt and ex hydrosulphite. After heating in steam the dis cluding therefrom other compounds formed dur charged pattern was white and free from a yel ing Said reaction, and separating said hydrolyzed lowish or brownish shade. Compound from said Solution. 75 When 4-amino-azo-benzene-4'-sulphonic acid 4. In a process for... manufacturing 4-amino- 5 2,139,325 3 aZO-benzene-4'-sulphonic acid, the steps which approximately within said temperature range Comprise adding the sodium salt of the Omega until 4-amino-azo-benzene-4'-Sulphonic acid is Sulphonic acid of 4-methyl-amino-azo-benzene formed. 4'-sulphonic acid to a solution of acid which is 6. A 4-amino-azo-benzene-4'-Sulphonic acid heated to about 95° C. to about 105° C. and con substantially identical with that which may be tains about 3 to 20 mols of hydrochloric acid per produced by coupling methyl-aniline-Omega mol of the Compound to be treated, and main taining the temperature of the reaction mixture Sodium sulphonate and diazotized sulphanilic acid approximately within said temperature range in a reaction medium, slowly and progressively O until 4-amino-azo-benzene-4'-Sulphonic acid is adding the coupling product and the reaction formed. medium in which it was formed to a hydrochloric O 5. In the process of manufacuring 4-amino acid solution which is heated to about 95 C. to azo-benzene-4'-sulphonic acid, the steps which about 100° C. and contains about 6 to about 20 comprise adding the sodium salt of the omega mols of hydrochloric acid per mol of the coupling 5 product, maintaining Said temperature during Sulphonic acid of 4-methyl-amino-azo-benzene the addition and for about 30 minutes after the 15. 4'-sulphonic acid to a solution of sulphuric acid addition is completed, cooling to about 60° C., which is heated to about 95° C. to about 105° C. filtering out the precipitate and Washing the and contains about 3 to 10 mols of Sulphuric acid Sane free of acid. per mol of compound to be treated, and main 20 taining the temperature of the reaction mixture CHAS. B. BISWE. WALTER W. WIRTH. 2